1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device of a mobile phone, which includes a sub memory.
2. Description of the Related Art
With the increase in mobile phone subscribers and the development of display technology, the mobile phone not only has a calling function but now includes various multimedia functions such as a camera function, a moving pictures display function, and a games function.
In addition, with the inclusion of multimedia functions the display device of the mobile phone has progressed from a light emitting diode (LED) device to a liquid crystal display (LCD) device and has changed from a black and white LCD to a color LCD. Furthermore, as the LCD window increases in size, a dual LCD folder type mobile phone has appeared with a main LCD window that can be closed and a sub LCD window that can operate on its own to reduce power consumption and protect the main LCD window.
Among mobile phones with multimedia functions one of the more popular functions is the camera function. The development of a mobile phone including a digital camera (e.g., a camera phone) has been delayed somewhat because of several factors such as unstable demand and supply, high price, and high power consumption. However, with the recent development of a mega pixel super extended graphics array (SXGA: 1280×1024) complementary metal oxide semiconductor (CMOS) image sensor, an increased supply of mega pixel camera phones has become a reality.
Although the resolution of camera phones is low at 300,000 pixels with a common intermediate format (CIF) (288×352) or video graphics array (VGA) (4802×6402), mega pixel camera phones have steadily spread throughout the world.
The appearance of mega pixel camera phones is not only a combination of the digital camera and mobile phone but also signals a change in paradigm. That is, with the emergence of mega pixel camera phones, ripple effects such as full-scale adoption of an application processor, the appearance of a high-resolution display device having a quarter video graphics array (QVGA) (320×240) or higher resolution, an increase in mobile phone memory capacity and acceleration of high-speed communication services simultaneously occur. In a similar case, when the poly sound phone was released, new services such as bell sound services and call connection sound services were provided.
With the inclusion of such application processors and display devices having resolutions greater than QVGA, the technology for reducing energy consumption in mobile phones and display drivers, which can realize various functions, has advanced.
After the communication service, code division multiple access 2000 (CDMA 2000) was introduced for mobile phones, various applications such as digital cameras, camcorders, LCDs, cards, memory, global positioning system (GPS)/Bluetooth, graphics/animation, and audio/sound have appeared for use with mobile phones leading to an overflow of the existing base band large scale integration (LSI) prompting the release of application processors that specialize in such applications.
The application processor of a mobile phone may be installed separately from the base band LSI or may be installed within the base band LSI. For example, a double-chip solution in which the application processor with necessary functions using the existing base band LSI can be installed separately from the base band LSI and is advantageous in that expansion, reduction, and diversification of various functions are easy and economical. However, because the double-chip solution uses two chips, an increase in substrate area for the two chips is inevitable.
A one-chip solution in which the application processor is installed inside the base band LSI provides compatibility between the base band LSI and application processor and individual environments thereof. However, the one-chip solution is disadvantageous in that it requires a high-priced integrated circuit (IC) with various functions beyond the needs of a mobile phone, and thus the expansion of multimedia functions is difficult.